‘I MISS sex all the time. I go for long periods without sex – like a camel,” Lauren Hutton proclaims between mouthfuls of crab soup at the trendy Midtown restaurant Michael’s.

It’s hard to believe that 56-year-old Hutton, whose gap-toothed grin made her one of modeling’s icons, is going through a Sahara-like dry spell.

“I could step outside and stick my finger in the air and men of all decades would come over; that’s not the problem,” says the blue-eyed siren, who’s casually – but elegantly – dressed in a green suit and green sneakers, with a pink cashmere sweater draped over her shoulders.

“The problem is, I don’t want to have sex with someone unless I’m intimate with them.

“I am looking for someone my own size, and it’s not easy to find. First of all, a lot of the good guys my age seem to be married. I also need to be with someone who has done a lot but who is curious about life, who is as optimistic and willing to learn and as young at heart as I am.

“But overall, I am pretty damn happy. You do not have to have a partner to be happy. I have lots of stuff to do until I find someone.”

Indeed, she does. Hutton – in town to promote her new diet book – is credited with changing the modeling industry not once but several times, riding the tides of fashion for the past three decades.

SHE has gone from ’70s supermodel to ’80s film actress to reborn ’90s model.

Perhaps her biggest contribution to a society where beautiful women are often shelved once they hit 30 has been her ability to reinvent herself, to help reduce much of the stigma of aging.

“Women aren’t useless after the age of 40,” she snorts. “We’re only useless if our job in life is to have children. And considering the fact that the world population is moving quickly up to seven billion we’ve got plenty of other things to do with our time.”

Hutton wasn’t always this accepting of aging. A real shock hit her 3 ½ years ago, when she realized she’d put on 25 pounds since age 30.

“I hadn’t been feeling as good about my body as I was used to,” the supermodel confesses. “I’d gone from 115 to 140 pounds. My body no longer felt the way it always had. It felt uncomfortable, like a heavy, ill-fitting suit of clothes. Photographers young enough to be my sons were asking me to suck in my stomach and stand sideways.”

Hutton claims her salvation came in an unexpected form – Slim-Fast. She was scuba diving in Micronesia when a friend told her he’d lost over 50 pounds using the plan.

Hutton says she started the program – two Slim-Fast shakes a day and a regular dinner – and shed her excess pounds in several months. It prompted her to write her new book, “The Slim-Fast Body Mind Life Makeover,” available this month in bookstores.

But while Hutton says she’s happy with her svelte figure, she says she’s disturbed by the super-skinny models she sees on the runways.

“It’s changed a great deal since the 1960s. The only model who was very thin back then was Twiggy,” Hutton recalls. “We all looked real; lean with muscle. Now the girls today are just bones without muscle. They’re going to be dogs when they are 29.

“I worry a lot about these girls. These agencies are taking children, kittens, and throwing them with sharks and wolves 20 or 30 years older.

“I’ve told many a mother who asks me how their 14-year-old daughter can become a model to wait until she’s finished college. Otherwise you might as well get a gun and shoot her.”

HUTTON didn’t start modeling until 1965 at the age of 22, after she’d had a few years of college at New Orleans’ Sophie Newcomb College, now a division of Tulane University.

She borrowed $200 from her mother and moved to New York City with the intention of booking passage to Africa on a steamer. Instead, she ended up modeling for Christian Dior, eventually landing with the prestigious Ford Modeling Agency.

But Hutton didn’t achieve success until the ripe old age of 31, when she landed a Revlon contract for a reported annual salary of $200,000.

“It was like falling into a ruby mine,” Hutton recalls. “I invented the cosmetics contract – that was what changed modeling from an hour business to a day business and a multimillion-dollar industry.”

Her career took a nosedive over the next decade with a series of B-list movies, including “American Gigolo,” opposite Richard Gere.

Hutton blames her 30-year relationship with investor Bob Williamson for her career downfalls. The two met soon after she moved to New York and spent years together summering in the Hamptons and circling the globe, traveling to exotic locales like Africa to satisfy Hutton’s wanderlust.

“I should have walked away after 10 years, but I didn’t have the courage,” Hutton says matter-of-factly. “I tanked my career in the 1980s simply because I took acting roles I shouldn’t have, just so I could spend time away from him. We loved each other, and in many ways we complemented each other, but it just wasn’t enough.”

Hutton finally got the courage to leave Williamson in 1989, after photographer Steve Meisel asked her to do a shoot for Barneys.

SUDDENLY, at 46, Hutton’s career was reborn. She began appearing in J. Crew ads and, more remarkably, negotiated another multiyear contract with Revlon in 1993.

“I thought it was important to help change a prejudice about American women,” Hutton says. “It doesn’t have to be over and out when you turn 40.”

Hutton credits her youthful glow in part to hormone replacement therapy and plastic surgery.

“I know hormone replacement therapy is controversial, and some doctors say it’s been linked to breast cancer, but it’s done wonders for me,” Hutton says. “I didn’t start taking it for about a year-and-a-half, and I sort of dried up. I actually shrunk an inch, to 5-6.”

She also has no issues with going under the knife.

“When I was around 40, I said I’d never get plastic surgery. I wouldn’t have a career now if I didn’t. I think it’s fine as long as you don’t look like a hard-boiled egg. The scariest thing would be to wake up and not like your face.”